Rules for Characters Exposing the Player To Dangerous Things

I think I might have narrowed it down to where it’s failing. I essentially tried to reverse engineer the extension to see how it works. What I find is that failure occurs when I reach this line:

@restoreundo rule;

That’s in the Hypo_Middle() function. Once that line is reached, the error mentioned above happens.

From what I can tell, this hasn’t worked for awhile. I found this comment from 2018:

I’m not sure if what was found there was the same issue but I too can’t get the example from the extension to compile.